Firstly, make sure that firewall is not enabled on your client machine. there is no other reason that Altiris Agent is not installed on client machines.
Secondly, for using WOL feature you need to set Power Management option from Altiris Agent setting for a particular collection.
Wake up on LAN is a feature provided by Notification Server not by DS.
For settings, open Altiris Console,
Settings > Agents / Plugins > Settings > Altiris Agent Settings - Targeted
Open the page, select the group of computers, on second half partiton, go to Advanced tab
check the option "Enable tickle on Altiris Agents"
the error messgae you are see is for special hardwares.
Also, Windows 2000 is not a supported OS by Deployment Solution 7.1